PortManager::find_free_port is updated

Asserts are added:
 - ports must be the "set"
 - exclude_ports must be iterable

Do not convert exclude_ports into "set" [optimization?]

Author: dmitry-lipetsk

testgres/helpers/port_manager.py

@@ -26,8 +26,11 @@ def find_free_port(self, ports: Optional[Set[int]] = None, exclude_ports: Option
         if ports is None:
             ports = set(range(1024, 65535))
 
+        assert type(ports) == set
+
         if exclude_ports is not None:
-            ports.difference_update(set(exclude_ports))
+            assert isinstance(exclude_ports, Iterable)
+            ports.difference_update(exclude_ports)
 
         sampled_ports = random.sample(tuple(ports), min(len(ports), 100))